AD7714
Temperature Measurement
Another application area for the AD7714 is in temperature
measurement. Figure 13 outlines a connection from a thermo-
couple to the AD7714. In this application, the AD7714 is oper-
ated in its buffered mode to allow large decoupling capacitors
on the front end to eliminate any noise pickup which there may
have been in the thermocouple leads. When the AD7714 is
operated in buffered mode, it has a reduced common-mode
range. In order to place the differential voltage from the thermo-
couple on a suitable common-mode voltage, the AIN2 input of
the AD7714 is biased up at the reference voltage, +2.5 V.
+5V
2
AV
DV
DD
DD
AV
DD
AD7714
THERMOCOUPLE
JUNCTION
1A
R
R
AIN1
AIN2
CHARGE BALANCING A/D
STANDBY
CONVERTER
C
C
AUTO-ZEROED
DIGITAL
FILTER
SYNC
AIN3
AIN4
AIN5
AIN6
⌺⌬
PGA
BUFFER
MODULATOR
A = 1–128
MCLK IN
CLOCK
GENERATION
1A
+5V
SERIAL INTERFACE
MCLK OUT
AGND
REGISTER BANK
+V
IN
REF IN (+)
RESET
V
OUT
AD780
GND
DRDY
REF IN (–)
AGND
POL
DGND
BUFFER
DOUT
DIN
SCLK
CS
DV
DD
Figure 13. Thermocouple Measurement Using the AD7714
REV. C
–35–
ADI [ ADI ]
